Siloxane polymers have unique properties derived mainly from the physical and chemical characteristics of the siloxane bond. These properties include low glass transition temperature, thermal and oxidative stability, resistance to ultraviolet radiation, low surface energy and hydrophobicity, high permeability to many gases, and biocompatibility. The siloxane polymers, however, often lack tensile strength.
The low tensile strength of the siloxane polymers can be improved by forming block copolymers. Some block copolymers contain a “soft” siloxane polymeric block or segment and any of a variety of “hard” blocks or segments. Polydiorganosiloxane polyamides and polydiorganosiloxane polyamides are exemplary block copolymers.
Mixtures of polymeric components have also been used in various applications. Enhanced peel adhesion performance has been seen when acrylic pressure sensitive adhesives have been melt mixed with thermoplastic elastomers and subsequently extrusion coated onto various substrates. Polydiorganosiloxane polyamide has been mixed in solvent with dielectric polymers to form dielectric layers for the imaging sheets of an electrostatic printing process that releases more easily from later applied toners. However, good images result only when the polydiorganosiloxane polyamide contains a non-polydiorganosiloxane hard segment of at least 50 weight percent. A need still exists for other polymeric mixtures having a variety of properties and applications.